UNIVERSITY  OF  CALIFORNIA 

COLLEGE    OF    AGRICULTURE 

AGRICULTURAL    EXPERIMENT    STATION 

BERKELEY,    CALIFORNIA 

CIRCULAR  305 

May,  1926 

LIMING  THE  SOIL 

P.  L.  HIBBARD* 


Two  thousand  years  ago,  the  Romans  knew  that  lime  increased  the 
productiveness  of  many  soils,  and  noAv  lime  is  one  of  the  most  fre- 
quently advised  soil  amendments.  In  the  humid  parts  of  the  United 
States,  lime  is  much  more  frequently  advantageous  than  in  California. 
The  soils  of  this  state,  in  most  places,  are  well  supplied  with  lime, 
yet  it  is  found  very  helpful  under  certain  conditions  on  some  soils. 

Today  the  progressive  farmer  would  like  to  have  answers  to  many 
questions,  such  as  the  following,  in  regard  to  the  use  of  lime : 

Why  do  some  soils  need  lime  while  others  do  not  ? 

Does  this  soil  need  lime? 

Will  it  pay  to  use  lime  on  this  soil? 

How  is  it  possible  to  find  out  what  will  be  the  effect  of  lime  on 
this  soil? 

What  becomes  of  lime  after  it  is  applied  to  the  soil? 

How  is  lime  lost  from  the  soil? 

What  kind  of  lime  is  best? 

Which  form  is  cheapest? 

Where  can  lime  be  obtained  ? 

How  may  one  find  out  the  quality  of  a  sample  of  lime? 

It  is  the  purpose  of  this  circular  to  answer  these  and  other  ques- 
tions, as  well  as  possible  in  the  light  of  present  scientific  and  practical 
knowledge.    Also,  some  suggestions  will  be  made. 


*  Credit  is  due  the  several  members  of  the  staff  of  the  College  of  Agriculture 
who  have  given  constructive  criticisms  during  the  preparation  of  this  circular. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


I.    GENERAL    STATEMENTS    AND    EXPLANATIONS 

In  everyday,  common  language,  the  word  "lime"  may  mean  any 
one  of  a  number  of  substances  which  are  sometimes  used  for  soil 
improvement,  and  "liming"  means  the  use  of  some  one  or  more  of 
these  materials  on  the  soil.  In  a  strictly  technical  sense,  only  calcium 
oxide  (CaO)  (quicklime),  or  calcium  hydroxide  (Ca(OH)2)  (slaked 
lime)  may  be  properly  spoken  of  as  lime.  For  the  present  purpose, 
the  word  "lime"  will  be  used  in  the  ordinary  sense,  meaning  any  one 
of  several  compounds  of  calcium  used  as  soil  amendments.  Gypsum 
is  not  to  be  considered  as  a  liming  material,  although  it  does  contain 
the  element  calcium,  and  is  often  of  great  value  as  a  soil  improver. 

Why  soils  need  lime. — It  is  common  knowledge  that  some  soils 
need,  or  are  improved  by  lime,  and  that  lime  applied  at  one  time  may, 
after  a  while,  become  ineffective.  Nearly  all  natural  waters  contain 
lime  which  has  been  dissolved  out  of  the  rocks  or  soil  over  which  the 
water  has  passed.  In  this  way,  the  soil  gradually  loses  its  lime,  which 
is  usually  carried  to  the  ocean,  where  it  is  deposited  and  becomes  lime- 
stone. By  this  process  have  originated  most  of  our  limestone  deposits 
now  used  in  industry  and  agriculture.  In  arid  regions  where  there 
is  little  leaching  by  rain,  there  is  usually  plenty  of  lime  in  the  soil, 
but  where  rainfall  is  heavy,  it  is  likely  to  be  deficient.  At  Ithaca, 
New  York,  the  loss  of  lime  by  leaching  has  been  found  to  be  as 
much  as  1000  pounds  an  acre  a  year,  and  similar  losses  have  been 
observed  in  other  places. 

All  agricultural  crops  absorb  lime  so  that  the  soil  is  gradually 
depleted  of  this  material  by  the  ordinary  removal  of  crops  from  the 
land.  However,  the  amount  of  lime  thus  carried  away  is  small  com- 
pared to  that  commonly  lost  by  leaching. 

Some  fertilizers,  for  example,  sodium  nitrate,  ammonium  sulfate, 
and  acid  phosphate,  tend  to  increase  this  loss.  Others,  such  as  bone 
meal,  calcium  cyanamid,  basic  slag  and  ordinary  manures,  increase 
the  supply.  The  greater  the  quantity  of  lime  applied  to  the  soil  at 
any  one  time,  the  more  rapid  will  be  its  loss  in  the  drainage  water. 

Soils  which  have  become  deficient  in  lime  are  frequently  called 
sour  or  acid.  But  perhaps  the  undesirable  properties  of  the  so-called 
sour  soils  are  more  frequently  due  to  a  lack  of  lime  than  to  the 
presence  of  injurious  acids.  Again,  some  acid  soils  may  contain 
sufficient  lime,  but  are  infertile  from  some  other  cause.  Certain  acid 
bog  soils  have  been  greatly  improved  in  productiveness  by  the  addition 


ClRO.  305]  LIMING   THE    SOIL  3 

of  phosphates  which  seem  to  produce  their  desirable  effect,  not  by 
neutralizing  acid  or  by  supplying  phosphate  as  fertilizer,  but  by 
chemically  removing  from  the  soil  moisture  poisonous  aluminum 
which  hinders  the  growth  of  crops.  Nevertheless,  in  most  cases,  all 
of  the  evils  which  may  be  included  under  the  term  "sour  soil"  are 
cured  by  lime. 

How  lime  is  retained  in  the  soil. — When  lime  in  any  form  is 
applied  to  the  soil,  it  is  probable  that  some  of  it  is  soon  converted  into 
silicates,  the  rest  into  carbonate.  The  latter  is  readily  dissolved  and 
carried  away  by  the  water  percolating  through  the  soil,  while  the 
silicates  of  lime  are  much  more  durable  in  the  soil,  though  they  also 
are  slowly  dissolved  and  washed  away.  Some  lime  is  combined  with 
the  humus  or  organic  matter  in  the  soil. 

How  lime  is  moved  about  in  the  soil. — Unless  it  is  dissolved  by 
water,  lime  moves  very  little  in  the  soil.  Heavy  applications  to  the 
surface  soil  have  not  penetrated  below  one  foot  in  many  years,  that 
is,  the  amount  of  lime  in  the  subsoil  is  not  much  increased  by  appli- 
cations to  the  surface.  When  the  lime  is  dissolved  by  water,  however, 
it  is  usually  carried  along  as  far  as  the  water  goes,  commonly  into 
the  drainage  and  thus  is  lost  to  the  land.  There  is  one  exception 
common  in  countries  of  low  rainfall.  When  the  rainwater  does  not 
penetrate  far  enough  to  get  into  the  drainage,  the  dissolved  lime  is 
likely  to  be  deposited  again  in  a  layer  at  the  lowest  point  to  which 
the  water  penetrates.  If  this  process  is  repeated  many  times  in  the 
course  of  years,  the  soil  materials  at  this  point  become  cemented 
together  by  the  lime  carbonate  and  silicate,  and  a  lime  hardpan  is 
formed.  When  once  formed,  the  hardpan  is  likely  to  remain  intact, 
unless  it  is  brought  to  the  surface  where  it  may  weather  down  into 
soil  once  more. 

Kinds  of  soils  improved  by  lime. — Practically  all  kinds  of  clayey 
or  heavy  soils  which  do  not  contain  much  lime  are  more  or  less 
benefited  by  lime,  and  loams  or  sands  having  little  lime  are  usually 
improved  by  liming.  Commonly,  but  not  always,  acid  soils  are  im- 
proved by  lime.  There  are  many  methods  of  testing  soils  to  deter- 
mine their  so-called  ' '  lime  requirement, ' '  but  none  of  them  are  always 
reliable.  Experience  is  the  only  sure  guide  to  show  whether  or  not 
lime  will  be  beneficial. 

Indications  of  plenty  or  lack  of  lime  in  the  soil. — Hard  well  water 
is  usually  a  good  indication  of  plenty  of  lime  in  the  soil,  while  soft 
water  is  commonly  found  when  lime  is  deficient.  Many  leguminous 
plants,  such  as  alfalfa  and  clover,  grow  well  in  soils  well  supplied 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

with  lime  but  not  in  soils  deficient  in  lime.  Sorrell  and  sour  dock 
grow  well  in  the  absence  of  lime,  but  also  may  prosper  in  well-limed 
soil. 

Only  an  actual  field  trial  can  show  with  certainty  whether  it  will 
pay  to  use  lime.  For  this  reason,  it  is  important  that  any  one  who 
is  uncertain  as  to  the  value  of  lime  on  his  land  should  first  confer 
with  the  local  farm  advisor.  The  latter  is  likely  to  know  whether 
lime  will  probably  be  a  paying  investment  on  the  soils  of  his  locality, 
and  will  give  specific  advice  about  how  and  when  to  apply  it.  The 
final  proof  of  the  value  of  lime  on  the  soil  is  found  in  an  increased 
yield  of  clover  or  alfalfa,  or  of  some  other  crop  in  the  rotation. 
Perhaps  it  may  be  merely  an  improvement  in  the  ease  of  tillage  and 
in  general  betterment  of  the  physical  condition  of  a  heavy  soil.  It  is 
sometimes  found,  however,  that  the  gain  in  increased  crops  or  in 
ease  of  tillage  does  not  equal  the  cost  of  liming. 

Lime  is  not  a  fertilizer. — Natural  limestones  in  many  cases  have 
been  partly  derived  from  decomposition  of  animal  remains,  so  that  in 
consequence  the  limestone  contains  a  small  amount  of  the  nitrogen 
and  phosphorus  of  the  animal.  However,  the  amount  of  these  plant 
foods  remaining  in  the  limestone  usually  is  so  small  that  it  is  of  little 
value.  Nevertheless,  some  ill-informed  dealers  may  present  to  their 
prospective  customer  a  chemical  analysis  showing  that  the  lime  they 
sell  contains  nitrogen,  phosphorus,  and  potash,  and  they  argue  that 
it  is  a  true  and  valuable  fertilizer.  The  percentage  of  these  plant 
foods  in  most  limestones  is  probably  less  than  in  good  fertile  soils. 
Limestone  or  other  lime  material  is  valuable  in  agriculture  almost 
solely  for  its  lime  content. 

Experience  has  shown  that  the  value  of  lime  is  usually  increased 
by  the  use  of  fertilizers,  and  also  that  fertilizers  are  most  effective 
when  lime  is  adequate.  The  reason  for  this  is  evident.  Anything 
that  increases  the  crop  produced  on  a  given  soil  increases  the  draft 
of  the  crop  on  the  plant  nutrients  in  the  soil,  thus  tending  to  exhaust 
the  soil  more  rapidly.  Consequently,  to  obtain  the  greatest  value 
from  fertilizers,  lime  should  be  adequate,  and  the  greatest  benefit 
from  lime  is  received  when  the  soil  is  well  fertilized. 


CIRC.  305]  LIMING   THE    SOIL 


IF.    EFFECTS   OF   LIME   ON   THE   SOIL 

Ordinary  fertile  soil  is  composed  chiefly  of  three  classes  of  sub- 
stances, besides  water — mineral,  organic,  and  biological.  The  mineral 
part  consists  mainly  of  rock  fragments  with  powdered  rock  and  clay. 
The  organic  portion  is  merely  the  remains  of  plants  and  animals. 
Though  small  in  amount,  this  portion  is  a  very  important  part  of  a 
good  soil.  The  biological  part  of  the  soil  is  also  very  essential.  It 
consists  of  the  microscopic  organisms  (bacteria,  protozoa,  molds,  etc.), 
also  insects,  worms  and  small  animals.  In  a  moist  soil,  all  these 
various  parts  are  surrounded  or  covered  by  a  film  of  water  which  is 
commonly  spoken  of  as  the  "soil  solution."  In  the  soil  solution  are 
dissolved  small  amounts  of  many  chemical  substances  known  as  salts, 
which  provide  the  mineral  elements  essential  for  plant  growth.  When 
lime  is  added  to  soil,  it  may  cause  changes  in  each  of  the  three  chief 
components,  the  mineral,  the  organic,  and  the  biological. 

Physical  changes  in  soil  produced  by  liming. — Clay  is  flocculated 
so  that  a  number  of  the  small  particles  become  united  into  a  single 
larger  one.  This  results  in  improvement  of  the  crumb  structure, 
and  in  the  lightening  of  heavy  soils  so  that  clay  becomes  less  sticky 
and  easier  to  work,  more  easily  penetrated  by  water  and  better 
drained,  and  hence  the  available  capillary  moisture  is  increased. 
This  tends  to  lengthen  the  growing  season  for  crops,  and  makes  injury 
from  drought  less  probable.  Usually  it  may  be  taken  for  granted 
without  any  kind  of  tests  that  heavy,  sticky  soils  will  be  physically 
improved  by  liming  so  that  the  growing  season  of  crops  will  be 
lengthened,  the  expense  of  cultivation  reduced  and  the  productiveness 
of  the  soil  increased.  All  these  tend  to  increase  the  money  value  of 
the  land.  It  is  reported  that,  at  the  Rothamstead  Experimental 
Station  in  England,  liming  a  heavy  soil  reduced  the  draft  in  plowing 
16  per  cent  and  increased  the  speed  of  traversing  the  field  26  per  cent. 
In  other  cases,  it  appears  that  improvement  in  ease  of  tillage  of  heavy 
soils  produced  by  liming  has  more  than  paid  for  the  cost  of  treat- 
ment by  a  reduction  in  the  cost  of  cultivation. 

Sandy  soils  are  improved  in  water-holding  capacity  by  liming. 
When  a  very  great  amount  of  lime  is  added  to  a  heavy  soil,  its  physical 
condition  is  profoundly  changed  so  that  it  no  longer  retains  its  clayey 
character.  Sands  also  are  greatly  modified  by  addition  of  large 
amounts  of  lime  so  that  they  become  similar  to  heavy  soils  which 
contain  much  lime.  A  soil  which  contains  much  lime  is  called  a 
marl,  or  a  marly  clay  or  a  marly  sandy  soil. 


b  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  chemical  changes  in  soil  caused  by  lime  are  commonly  called 
"sweetening."  Soil  acids  are  neutralized  and  harmful  conditions 
frequently  associated  with  these  acids  are  avoided.  When  the  soil 
contains  sufficient  lime  to  make  it  neutral  or  slightly  alkaline,  salts 
of  iron,  aluminum  and  manganese  cannot  dissolve  in  the  soil  solution 
in  amounts  sufficient  to  be  poisonous  to  plants.  Under  these  condi- 
tions, also,  the  phosphorus  of  added  fertilizers  is  less  likely  to  form 
unavailable  compounds  with  aluminum  or  iron. 

A  desirable  exchange  of  bases  in  the  soil  zeolites  (a  clay-like 
portion  of  the  soil)  is  sometimes  promoted  by  lime,  so  that  lime  is 
absorbed  and  potassium  is  released  for  the  nutrition  of  plants. 
Whether  this  change  is  of  much  practical  value  is  still  an  unsettled 
question. 

Deflocculation  and  running  together  of  clay,  which  may  occur 
in  the  absence  of  lime,  is  prevented  by  plenty  of  lime.  Deflocculation 
means  the  breaking  up  of  the  compound  soil  crumbs  into  the  much 
smaller  particles  of  clay.  These  very  fine  particles  are  what  give 
clay  its  "clayey"  character. 

All  forms  of  lime  have  finally  much  the  same  effect  on  soils,  but 
when  first  applied  there  is  some  difference  between  the  effects  of 
caustic  and  of  carbonate  forms.  The  caustic  or  quicklime  forms  are 
much  more  soluble  in  water  and  therefore  produce  their  effects  on 
the  soil  much  more  quickly  than  the  carbonate  of  lime  which  is  but 
slightly  soluble  in  water.  Consequently  some  form  of  caustic  lime  is 
preferred  when  it  is  desired  to  improve  a  clay  soil  quickly,  although 
carbonate  forms  of  lime,  when  ground  very  fine,  act  almost  as  rapidly 
as  caustic  lime.  The  somewhat  common  belief  that  the  use  of  quick- 
lime on  the  soil  causes  more  rapid  destruction  of  organic  matter  than 
carbonate  of  lime,  has  been  shown  to  have  little  foundation  in  fact. 

Alkali  soils  may  be  affected  in  two  quite  different  ways  by  lime. 
In  the  presence  of  much  white  alkali  (sodium  salts)  lime  sometimes 
causes  formation  of  the  very  injurious  black  alkali.  When,  however, 
a  soil  contains  black  alkali  with  only  a  little  white  alkali,  lime, 
together  with  decaying  vegetable  matter,  tends  slowly  to  neutralize 
and  remove  the  black  alkali.  For  overcoming  black  alkali,  however, 
gypsum  is  much  more  effective  than  lime. 

Biological  effects  of  liming. — Fertile  soils  harbor  vast  numbers  of 
bacteria  and  other  micro-organisms  which  subsist  on  the  vegetable 
and  animal  substances  in  the  soil,  changing  them  so  that  crop  plants 
can  obtain  nutriment  from  them.  This  decomposition  process  is  com- 
monly spoken  of  as  "  production  of  humus. ' '    Insufficient  lime  favors 


ClRO.  305]  LIMING    THE    SOIL  7 

the  growth  of  objectionable  bacteria  which  produce  undesirable  or 
poisonous  products.  Plenty  of  lime  favors  the  growth  of  desirable 
bacteria  and  this  growth  causes  changes  which  benefit  crop  plants 
by  accelerating  oxidation  of  organic  matter  and  destroying  poisonous 
substances. 

The  two  most  important  of  these  changes  are  ammonification,  by 
which  the  nitrogen  in  organic  materials  is  changed  into  ammonia; 
and  nitrification,  the  change  by  which  ammonia  is  converted  to 
nitrate,  the  form  in  which  most  plants  take  up  their  nitrogen.  Fix- 
ation of  nitrogen  from  the  air  so  that  it  becomes  available  to  plants, 
also  requires  lime  in  the  soil  to  make  conditions  suitable  for  nitrogen- 
fixing  (symbiotic)  bacteria. 

On  the  other  hand  some  undesirable  organisms  of  the  soil  are 
favored  by  plenty  of  lime.  Such  is  the  fungus  which  causes  potato 
scab.  This  potato  disease  is  much  less  injurious  in  an  acid  soil. 
Excessive  lime  favors  "root  rot"  of  tobacco,  a  fungous  disease,  but 
it  reduces  activity  of  another  fungus,  the  "finger  and  toe  disease" 
of  cabbage  and  similar  plants. 

Lime  is  an  essential  element  in  plant  nutrition.  For  this  need, 
most  soils  probably  contain  enough  lime.  Too  much  lime  in  some  of 
our  California  soils  is  associated  with  a  diseased  condition  known 
as  chlorosis  which  affects  certain  plants.  No  satisfactory  treatment 
of  soil  for  this  trouble  is  known.  Probably  it  is  rarely  or  never 
caused  by  artificial  addition  of  lime. 

Experiments  have  shown  that  plants  grown  with  plenty  of  lime 
in  the  soil  are  much  richer  in  lime  than  those  grown  in  soils  where 
lime  is  deficient.  A  deficiency  of  lime  in  plants,  such  as  alfalfa,  seems 
to  be  caused  by  the  presence  of  black  alkali  in  the  soil,  so  that  although 
the  soil  may  contain  much  lime,  it  is  not  available  to  the  plant. 
Experiments  are  being  conducted  to  find  a  method  of  correcting  such 
conditions. 

III.    EFFECT  ON   CROPS  OF   LIMING   THE   SOIL 

Besides  the  already  mentioned  more  or  less  indirect  effects  on 
plants  which  are  caused  by  liming  the  soil,  some  more  direct  effects 
must  be  considered.  Some  plants  grow  much  better  in  the  presence 
of  plenty  of  lime,  others  succeed  better  in  acid  soils.  In  the  former 
class  are  the  legumes  such  as  alfalfa,  red  and  white  clover,  soy  beans, 
peas,  alsike  clover,  cowpeas,  vetch  and  field  beans.  Blueberries,  water- 
melons, rhododendrons,  and  cranberries,  on  the  contrary,  seem  to  be 
injured  by  soil  conditions  associated  with  large  quantities  of  lime. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


IV.    FORMS    OF    LIME*    FOR    AGRICULTURAL    USE 

The  better  grades  of  lime  materials  are  likely  to  be  used  in  trade 
and  industry,  leaving  for  agricultural  use  only  the  poorer  grades 
which  vary  greatly  in  purity. 

The  substances  other  than  lime  contained  in  the  low  grade 
materials  are  usually  of  little  value  in  the  soil.  The  three  principal 
forms  of  lime  materials  as  regards  chemical  composition,  are  oxide, 
hydrate,  and  carbonate. 

The  carbonate  form  is  found  naturally  as  marble,  limestone  rock, 
marl  (which  is  unconsolidated  limestone  mixed  with  more  or  less  clay 
and  sand),  shells  (such  as  those  of  oysters  or  clams),  or  as  by-products 
of  manufacturing  such  as  air-slaked  lime,  sugar  factory  waste  lime, 
and  ashes  of  some  kinds.  All  of  the  carbonate  forms  are  relatively 
inert  and  may  be  applied  to  the  soil  in  almost  any  amount  without 
direct  injury  to  plants. 

The  oxide  and  hydrate  of  lime  are  commonly  spoken  of  as  caustic 
limes.  They  may  cause  temporary  injury  to  vegetation  if  applied 
to  growing  plants  in  large  quantities.  After  some  days  or  perhaps 
weeks  in  the  soil,  however,  the  caustic  forms  become  converted  to 
carbonate  or  silicate,  thus  losing  their  caustic  properties.  Caustic 
lime  is  the  ordinary  lime  used  in  building,  known  as  burnt,  lump,  or 
quicklime.  It  is  made  by  burning  carbonate  of  lime  at  red  heat, 
whereby  the  carbon  dioxide  or  carbonic  acid  of  the  carbonate  is  driven 
off  and  calcium  oxide,  oxide  of  lime,  remains.  When  exposed  to  the 
air,  the  oxide  or  hydrate  takes  up  carbon  dioxide  from  the  air  and 
again  becomes  carbonate,  which  is  then  known  as  air-slaked  lime. 

Hydrated  lime  is  made  by  adding  to  quicklime  somewhat  less  than 
half  its  weight  of  water.  The  water  is  taken  into  chemical  combina- 
tion with  the  lime  and  the  lumps  of  quicklime  fall  to  a  fine  dry 
powder,  hydrated  lime.  This  form  of  lime,  mixed  with  uncombined 
water,  is  found  in  various  waste  products,  such  as  acetylene  waste 
lime  from  carbide  gas  generators,  tannery  waste  lime  and  gas-house 
waste  lime.  Acetylene  waste  lime  and  gas-house  waste  lime  are  likely 
to  contain  poisonous  substances  which  are  injurious  to  plants.  For 
this  reason,  these  limes  should  not  be  used  on  the  soil  at  a  time  when 
tender  plants  are  growing.  After  these  limes  have  been  exposed  to 
the  air  and  moisture  in  the  soil,  the  poisonous  substances  disappear. 
Then  the  lime  is  as  good  as  an  equivalent  amount  of  any  other  lime. 


*  In  this  discussion,  gypsum  is  not  regarded  as  a  lime  material. 


Circ.  305] 


LIMING    THE    SOIL 


Magnesium  limes  are  any  one  of  the  above-mentioned  forms  which 
contain  more  or  less  magnesium.  Natural  magnesium  limestone  is 
called  dolomite.  Magnesium  limes  are  usually  equal  or  greater  in 
value  agriculturally  than  pure  limes,  except  that  their  action  is  slower. 

Phosphates  of  lime,  such  as  bone  meal,  basic  slag,  and  lime- 
nitrogen,  or  calcium  cyanamide,  have  some  value  as  lime  materials, 
in  addition  to  their  content  of  phosphate  or  nitrogen  to  which  they 
owe  their  chief  value.  Still  another  form  of  lime  which  has  some 
agricultural  value  is  the  silicate  which  is  a  component  of  many 
natural  rocks.  It  is  not  an  ordinary  article  of  commerce,  but  may 
be  made  artificially. 

TABLE  l* 

Approximate  Quantities  of  Total  and  Available  Oxides  of  Lime 
in  One  Ton  of  Liming  Material 


Market  material 


Limestone,  fine,  1/60  in.  mesh 

Limestone,  fine,  1/60  in.  mesh,  impure. 

Limestone,  coarse,  1/8  in.  mesh 

Gas  house  lime 

Beet  sugar  lime 


Total  oxides 


Per  cent 


52 
45 
52 
35 
39 


Pounds 
(per  ton) 


1040 
920 

1040 
700 
780 


Available  oxides 


Per  cent 


100 

100 

50 

50 

100 


Pounds 
(per  ton) 


1040 
920 
520 
350 

780 


Lump  lime,  pure 

Lump  lime,  impure.. 
Quick  lime,  ground. 


85 
90 


1960 
1700 
1800 


90 
70 
96 


1764 
1190 
1728 


Hydrated  lime. 


75 


1500 


100 


1500 


*  Data  from  National  Lime  Assn.,  Trade  Bui.  102,  Washington,  D.  C. 

All  of  the  forms  of  lime  differ  greatly  in  value,  because  of  the 
varying  degrees  of  purity  of  the  natural  rock  from  which  they  are 
derived.  Also,  the  amount  of  water  in  the  hydrated  forms  varies 
greatly  so  that  they  do  not  have  any  very  definite  composition.  The 
most  practical  measure  of  value  of  lime  is  its  power  of  neutralizing 
acids.  When  quite  pure,  56  pounds  of  oxide,  74  pounds  of  hydrate 
and  100  pounds  of  carbonate  have  equal  neutralizing  powers.  Or, 
roughly,  one  ton  of  carbonate  is  equalled  by  three-quarters  of  a  ton 
of  hydrate,  or  one-half  ton  of  oxide  of  lime.  Table  1  shows  the 
relative  lime  value  of  different  liming  materials. 

Importance  of  fineness. — The  agricultural  availability  or  effective- 
ness of  the  various  forms  of  lime  is  largely  dependent  on  the  purity 


10  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

and  fineness  of  the  particles.  The  purer  and  the  finer  the  lime  the 
more  rapidly  will  it  act.  Very  impure  lime  is  slow  to  react  with  the 
soil  acids,  besides  having  deficient  liming  power.  The  coarser  the 
particles  of  the  lime  material,  the  less  easily  will  it  become  thoroughly 
mixed  with  the  soil,  the  slower  will  be  its  action  and  also  the  longer 
will  it  last.  Limestone  particles  of  from  10  to  20  mesh  size  may  last 
for  10  years  in  the  soil  without  producing  much  effect.  Such  material 
cannot  be  considered  as  available  lime. 

Ground  limestone  which  will  pass  a  60-mesh  sieve  is  fine  enough 
to  be  almost  as  effective  as  the  caustic  forms.  The  latter  are  extremely 
fine  by  reason  of  the  method  of  their  preparation.  Sugar  house  waste 
lime  is  peculiarly  well  adapted  to  agricultural  use  on  account  of  its 
extreme  fineness.  It  is  one  of  the  carbonate  forms  of  lime.  It  also 
contains  small  amounts  of  nitrogen,  potash  and  phosphorus,  so  that 
it  acts  to  a  small  extent  as  a  fertilizer  as  well  as  a  lime  material. 

For  equal  neutralizing  effect,  there  is  considerable  difference  in 
cost  between  the  various  forms  of  lime  and  this  difference  will  vary 
with  the  locality.  Since  the  value  of  a  lime  material  is  best  measured 
by  its  power  to  neutralize  soil  acids,  the  farmer  should  endeavor  to 
buy  that  form  which  will  supply  the  most  neutralizing  power  to  his 
soil  for  a  dollar. 

To  determine  which  form  will  give  the  most  for  the  money,  it  is 
necessary  to  know  the  cost  of  (1)  a  unit  of  lime  at  the  plant  or  the 
dealers,  (2)  freight,  (3)  wagon  haul,  and,  (4)  spreading.  The  cost 
of  (1)  may  not  be  the  chief  cost.  The  cost  of  (2),  (3)  and  (4)  may 
be  reducd  by  using  higher  purity  or  more  concentrated  forms.  Haul- 
ing cost  (3)  may  be  a  large  proportion  of  the  total.  It  may  run  from 
50  cents  a  ton  for  one  mile,  up  to  three  dollars  a  ton  for  ten  miles. 
An  ordinary  case  might  be  as  follows,  for  one  application  of  two  tons 
ground  limestone  per  acre : 

First  cost,  including  freight,  two  tons  @  $3.50  per  ton $7.00 

Wagon  haul,  five  miles 3.20 

Spreading  on  the  land 1.05 

Total  cost  per  acre $11.25 

The  following  table  gives  a  more  complete  statement  of  estimated 
items  of  costs  of  liming  materials  delivered  on  the  farm. 

When  this  method  of  computation  is  employed,  results  often 
surprising  to  the  farmer  are  secured.  Indeed,  the  material  that 
appeared  cheapest  to  him  based  upon  the  quotation  at  the  factory  or 
at  the  station,  may  often  prove  to  be  comparatively  expensive. 


Ciro.  305] 


LIMING    THE    SOIL 


11 


TABLE  2f 
Factors  of  Cost  of  Lime  Delivered  at  the  Farm 


Cost  at 

kiln  or 

mill  in 

bulk 


Cost  of 
bagging 
or  extra 
handling 


Expense 

of  freight 

100 

miles 


Expense 

of  wagon 

haul 

6  miles 


Approximate  total 
cost  at  farm 


Per 

gross 


Per  100 

lbs.  of 

available 

oxides 


Limestone,  fine,  1/60  in 
mesh 

Limestone,  fine,  1/60  in 
mesh,  impure 

Limestone,  coarse,  1/8  in 
mesh 

Gas  house  lime 

Lump  lime,  pure 

Lump  lime,  impure 

Quicklime,  ground 

Hydrated  lime 


$3.50 

2.75 

2.00 
.50 


$1.75 

1.75 

1.75 
1.00 


$1.40 

1.40 

1.40 
1.40 


$2.50 

2.50 

2.50 
2.50 


$9.16 

8.40 

7.65 
5.40 


8.50 
6.00 
8.00 

10.00 


2.50* 
2.50* 
2.00 


1.75 
1.75 
1.75 


2.50 
2.50 
2.50 


15.25 
12.75 
14.25 


2.50 


1.75 


2.50 


16.75 


$0,880 

0.913 

1.471 
1.543 


0.865 
1.071 
0.825 


1.116 


*  Fifty  cents  allowed  for  slaking. 

f  From  National  Lime  Assn.,  Trade  Bui.  102,  Washington,  D. 


These  figures  are  not  to  be  regarded  as  actual  costs  since  they  will 
vary  widely,  depending  on  local  conditions,  but  rather  as  approximate 
values  used  to  illustrate  the  method  of  computation  and  which  may 
be  substituted  by  actual  costs.  They  indicate  rather  the  method  of 
calculating  the  cost  for  any  form  of  liming  material,  and  enable  the 
buyer  to  figure  in  which  form  he  can  get  the  most  lime  value  for  his 
money.  The  retail  price  of  ground  limestone  at  the  dealers  may  vary 
from  one  to  ten  dollars  per  ton  at  different  places  in  California.  The 
market  price  evidently  cannot  be  considered  as  a  measure  of  value  of 
the  material  on  the  farm.  Since  the  acid  neutralizing  power  of 
various  forms  of  lime  of  different  degrees  of  purity  varies  so  greatly, 
it  would  seem  best  to  buy  lime  material  by  the  unit  (which  is  1  per 
cent  of  a  ton  or  20  lbs.)  of  oxide  of  lime  rather  than  by  the  ton  or 
other  unit  of  weight. 


12  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 


V.    SOURCES   OF  AGRICULTURAL   LIMESTONE 

The  three  chief  sources  through  which  ground  limestone  may  be 
secured  are  the  regular  dealers,  the  farmers'  association  and  the  indi- 
vidual farmer.  When  demand  is  small,  the  regular  dealer  will  supply 
it  at  a  profit  to  himself  and  usually  at  a  relatively  high  price. 

The  following  is  a  list  of  the  chief  dealers  in  lime  in  California : 


EEGISTERED  DEALEES  IN  AGRICULTURAL   LIME,   FOR   THE   FISCAL 
YEAR  ENDING  JUNE  30,  1925 

(From  Special  Publication  No.  52,  Department  of  Agriculture,  State  of  Cali- 
fornia, on  Commercial  Fertilizers,  Agricultural  Minerals,  1924.) 

Agricultural  Lime  and  Compost  Company,  485  California  street,  San  Francisco, 

Calif. 
Bernal  Marl  Fertilizer  Company,  207  South  First  street,  San  Jose,  Calif. 
A.  M.  Blumer,  433  California  street,  San  Francisco,  Calif. 
California  Associate  Buyers  Company,  153  Broadway,  Fresno,  Calif. 
California  Lime  Company,  Fortieth  and  Opal  streets,  Oakland,  Calif. 
California    Portland    Cement    Company,    1228    Pacific    Mutual    Building,    Los 

Angeles,  Calif. 
El  Dorado  Lime  and  Minerals  Company,  Shingle,  Calif. 
E-Z-Way  Company,  955  Sixty-first  street,  Oakland,  Calif. 
Grand  Canyon  Lime  and  Cement  Company,  840  Commercial  street,  Los  Angeles, 

Calif. 
Holmes  Lime  and  Cement  Company,  2  Pine  street,  San  Francisco,  Calif. 
Horton  Lime  Company,  681  Market  street,  San  Francisco,  Calif. 
Kaweah  Quarries,  Lemon  Cove,  Calif. 

Arthur  F.  Levitt,  411  South  Main  street,  Los  Angeles,  Calif. 
H.  B.  Matthews,  466  Jackson  street,  Pasadena,  Calif. 
Mount  Diablo  Lime  Marl  Company,  Walnut  Creek,  Calif. 
Nevada  Lime  and  Rock  Company,  846  Commercial  street,  Los  Angeles,  Calif. 
Nitrate  Fertilizer  Company,  754  South  Maple  street,  Los  Angeles,  Calif. 
Pacific  Guano  and  Fertilizer  Company,  Matson  Building,  San  Francisco,  Calif. 
Pacific  Lime  and  Plaster  Company,  58  Sutter  street,  San  Francisco,  Calif. 
Pacific  Limestone  Products  Company,  25  King  street,  Santa  Cruz,  Calif. 
Pacific   Portland  Cement   Company,   Consolidated,   827    Pacific   Building,   San 

Francisco,  Calif. 
Pennewell  and  Company,  Lemon  Cove,  Calif. 

Pep  Chemical  Company,  Alameda  and  Southern  Pacific  tracks,  Burbank,  Calif. 
Torrance  Lime  and  Fertilizer  Company,  301  Bradbury  Building,  Los  Angeles, 

Calif. 
Union  Lime  Company,  3220  San  Fernando  road,  Los  Angeles,  Calif. 


ClRO.  305]  LIMING   THE    SOIL  13 

Farmers'  associations  in  some  places  have  been  able  to  supply 
their  members  with  ground  limestone  at  much  lower  cost  than  dealers ' 
prices.  These  associations  are  formed  where  there  is  a  demand  for 
considerable  lime.  They  set  up  a  plant  for  grinding  limestone  which 
is  usually  obtained  from  some  local  quarry.  Thus,  if  the  association 
is  well  managed,  the  members  will  get  their  limestone  at  the  lowest 
possible  cost.  By  arranging  so  that  all  do  not  want  the  lime  delivered 
at  the  same  time,  a  relatively  small  plant  may  be  able  to  supply  a 
large  amount  of  material.  Some  of  the  ground  limestone  could  be 
stored  during  times  when  farmers  were  busy  with  other  work,  so 
that  when  the  demand  for  lime  is  great  it  could  be  quickly  supplied. 
One  successful  plan  consists  in  using  a  portable  grinder  which  can 
be  taken  to  the  place  where  lime  is  wanted.  The  individual  farmer 
may,  in  some  cases,  have  his  own  outfit  for  supplying  his  own  needs, 
and  perhaps  those  of  some  of  his  neighbors. 

Perhaps  one  of  the  main  reasons  why  lime  is  not  more  frequently 
used  on  the  soil  is  that  it  is  not  a  retail  commodity  which  can  always 
be  obtained  in  any  amount  when  it  is  wanted.  If  it  could  be  had 
more  cheaply  and  conveniently,  probably  much  more  lime  would  be 
used. 


VI.    APPLICATION   OF   LIME   TO  THE   SOIL 

At  what  time  should  lime  be  supplied  to  the  soil? — So  far  as  the 
soil  is  concerned,  it  makes  little  difference  when  lime  is  applied. 
Caustic  lime  should  not  be  applied  while  any  tender  crop  is  growing. 
Otherwise,  lime  may  be  applied  at  any  time  when  it  is  most  con- 
venient. Since  the  lime  must  be  well  worked  into  the  soil  to  produce 
the  desired  effect,  it  is  evident  that  this  can  be  done  best  on  plowed 
ground  so  that  the  lime  will  be  stirred  into  the  soil  by  harrowing. 
On  meadows  or  pastures,  lime  may  be  spread  on  top  of  the  ground, 
probably  most  advantageously  during  the  winter  when  the  grass  is 
not  growing  much. 

How  lime  may  be  spread  on  the  soil. — One  common  way  is  to 
throw  it  by  shovels  from  a  wagon  as  it  is  driven  across  the  field.  This 
is  likely  to  result  in  uneven  application.  A  better  method  is  to  dis- 
tribute lime  from  a  machine  somewhat  like  a  grain  drill,  which  makes 
a  uniform  application.  Such  machines  may  be  bought  of  dealers  or 
contrived  from  materials  on  the  farm. 

Amount  of  lime  to  be  used. — In  the  past,  large  applications  at  one 
time  have  been  recommended,  enough  to  completely  neutralize  the 


14  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

soil  acidity.  Now  it  is  known  that  it  is  not  necessary  to  neutralize  all 
the  soil  acidity,  so  that  smaller  and  more  frequent  applications  are 
more  economical  and  perhaps  more  effective.  On  any  but  the  most 
acid  soils,  500  pounds  an  acre  every  year  or  two  is  likely  to  be  suf- 
ficient. Since  some  crops  need  less  lime  than  others,  the  lime  should 
be  used  just  prior  to  that  crop  in  the  rotation  which  needs  the  most 
lime.  As  a  general  statement,  it  may  be  said  that  enough  lime  should 
be  used  so  that  it  is  never  a  limiting  factor  in  crop  production,  pro- 
vided that  the  cost  is  not  greater  than  the  value  of  increased  crops 
produced.  If,  however,  the  lime  is  used  to  improve  the  texture  of 
a  heavy  soil,  much  larger  amounts  may  be  needed  to  produce  the 
desired  effect. 

A  New  Jersey  example  shows  the  economic  advantage  of  light 
over  heavy  liming.  During  a  15-year  test,  one-half  ton  of  ground 
limestone  to  the  acre  annually  yielded  the  same  crop  increase  as  an 
application  of  two  tons  to  the  acre.  That  is,  where  two  tons  to  the 
acre  were  used,  three-quarters  of  it  gave  no  increased  returns. 

Light  liming  is  to  be  recommended  when  it  is  needed  chiefly  to 
supply  lime  as  a  plant  food,  for  which  heavy  liming  is  needless.  Even 
where  heavy  applications  are  needed  for  improving  the  physical  con- 
dition of  the  soil,  heavier  liming  than  is  necessary  should  be  avoided 
because  the  losses  by  natural  processes  are  proportional  to  the  amount 
of  lime  added. 

Another  advantage  of  light  liming  is  that  it  fits  in  with  the  other 
farm  work  more  easily  than  heavy  liming,  since  the  latter  is  such  a 
big  job  that  it  cannot  be  done  at  any  time  when  regular  farm  work 
is  pressing. 

Kind  of  lime  to  be  used. — On  sandy  soils  which  are  liable  to  be 
deficient  in  organic  matter,  one  of  the  carbonate  forms  is  preferable 
to  any  of  the  caustic  forms  of  lime.  For  heavy  soils  on  which  lime  is 
valuable  chiefly  as  a  means  of  improving  the  physical  conditions 
caustic  lime  will  give  a  quicker  response,  owing  to  its  greater  solu- 
bility in  water.  Aside  from  these  specific  recommendations,  the  choice 
of  the  kind  of  lime  to  use  may  depend  on  economic  conditions  chiefly. 
It  would  seem  best  to  use  that  form  of  lime  which  will  supply  the 
most  actual  lime,  that  is,  the  greatest  neutralizing  power,  for  a  dollar. 
This  will  depend  on  (a)  chemical  equivalent,  that  is,  actual  lime 
supplied,  (&)  cost  of  a  ton  or  other  unit,  (c)  freight  cost,  (d)  cost 
of  hauling  and  application. 


ClRO.  305]  LIMING   THE    SOIL  15 

Lyon  and  Buckman*  give  the  following  example  to  illustrate  the 
point : 

Suppose  slaked  lime,  70  per  cent  CaO,  sells  at  $8.00  a  ton,  and  ground  lime- 
stone, 50  per  cent  CaO,  costs  $4.50  a  ton,  and  the  freight  charge  is  $3.00  a  ton, 
hauling  and  spreading  $1.00  a  ton. 

Then  1  ton  of  slaked  lime  would  cost  $8  +  $3  +  $1  =  $12  on  the  soil. 

To  furnish  the  same  amount  of  actual  lime,  CaO,  in  the  form  of  the  ground 
limestone,  would  require  1.4  tons,  which  would  cost  $6.30  -f-  $4.20  +  $1.40  e=  $11.90. 
In  this  example,  the  difference  between  the  two  forms  is  slight.  Lower  cost  of 
freight  or  hauling  would  give  the  ground  limestone  still  further  advantage,  while 
increasing  these  charges  would  make  it  cheaper  to  use  the  slaked  lime. 

Evidently,  every  farmer  should  calculate  for  himself  which  will 
be  the  cheaper  form  of  lime,  giving*  due  consideration  to  each  of  the 
separate  items  of  cost. 

VII.    LOCALITIES    IN    CALIFORNIA  WHERE    LIME    IS    LIKELY   TO    BE 

BENEFICIAL 

A  large  proportion  of  California  soils  contain  enough  lime  so  that 
further  applications  are  not  likely  to  be  advantageous.  Relatively, 
only  a  small  portion  of  our  soils  may  be  called  sour.  Heavy  clay  or 
adobe  soils,  however,  are  usually  improved  in  physical  character  by 
liming. 

Lime  is  more  or  less  helpful  in  parts  of  the  northern  coast  counties 
and  to  some  extent  south  of  San  Francisco  Bay,  in  a  good  deal  of  the 
Sierra  Nevada  foothills  on  the  east  side  of  the  great  interior  valley, 
and  in  various  places  throughout  the  valley.  South  of  the  Tehachapi, 
lime  is  not  usually  needed. 

VIII.     STATE    INSPECTION    AND    ANALYSIS    OF    LIME    MATERIALS 

Some  years  ago,  much  very  inferior  lime  was  sold  for  the  price 
of  good  material.  To  protect  the  public  in  this  matter,  the  sale  of 
agricultural  minerals,  including  all  forms  of  lime,  was  placed  in 
charge  of  the  State  Fertilizer  Control  in  1923.  That  office  now  makes 
regular  inspections  and  analyses  of  minerals  offered  for  sale,  and 
takes  care  that  the  dealers  shall  supply  goods  of  the  quality  they 
guarantee.  Any  farmer  may  have  his  lime  analyzed  by  the  Fertilizer 
Control  at  small  cost,  and  so  may  be  sure  of  the  quality  of  the  lime 
he  is  buying.  Application  should  be  made  to  the  Bureau  of  Chem- 
istry, State  Department  of  Agriculture,  at  Sacramento. 


*  Lyon,  T.  L.,  and  H.  O.  Buckman,  The  nature  and  properties  of  soils,  p.  368. 
(Macmillan  Company,  New  York,  1922.) 


15m-5,'26 


